Bankrupt German carrier airberlin’s administrator is seeking damages of up to €2 billion ($2.28 billion) from former majority shareholder Etihad Airways.

A Berlin court revealed in a Dec. 14 statement that it had received a claim from airberlin’s creditors for damages against Etihad that could run to as much as €2 billion.

The claim relates to a letter dated April 28, 2017, in which the administrator said Etihad had agreed to “provide airberlin with the necessary support for the next 18 months, in order to enable its subsidiary to meet its financial obligations.”

The court’s statement said the administrator believed that, “contrary to this commitment, [Etihad] withdrew airberlin’s financial support in August 2017, with the result that airberlin had to file for bankruptcy.”

Etihad has vowed to fight the claim. A spokesperson for the Abu Dhabi-based carrier said: “We confirm that we have received a claim filed at the Berlin Regional Court by the insolvency administrator of airberlin. We believe that the claim is without merit and will defend ourselves vigorously against it. Furthermore, we will not comment publicly on this issue at this time.”

Etihad acquired a 29% stake in airberlin in 2011 as part of a strategy to increase its global presence by buying into foreign airlines. Rather than investing in financially successful carriers, however, Etihad bought stakes in struggling European operators.

In addition to its airberlin stake, the Middle Eastern carrier took a 49% stake in Alitalia, which went on to file for bankruptcy protection in 2017. It also invested in Swiss regional carrier Darwin Airline, which it rebranded as Etihad Regional, before selling it to Slovenia’s Adria Airways.